public string Execute()
{
primes = new HashSet <long>(Primes.GeneratePrimes(1, 20000));
var highestYield = 0;
var bestA = 0;
var bestB = 0;
var range = 1000;
for (var a = -range; a < range; a++)
{
for (var b = -range; b <= range; b++)
{
var total = CalculatePrimes(a, b);
if (total > highestYield)
{
bestA = a;
bestB = b;
highestYield = total;
}
}
}
return((bestA * bestB).ToString());
}
public void primes_first_10_numbers()
{
var actual = Primes.GeneratePrimes(10);
var expected = Primes.WritePrimes(10);
Assert.IsTrue(ElementsOnListsAreTheSame(actual, expected));
}
public string Execute()
{
var maximum = 28123;
var primes = new HashSet <long>(Primes.GeneratePrimes(1, maximum));
abundantValues = new HashSet <long>();
for (var i = 1; i <= maximum; i++)
{
if (!primes.Contains(i))
{
var div = Utility.GetDistinctDivisors(i);
var sum = div.Sum();
if (sum > i)
{
var abundant = i;
abundantValues.Add(i);
}
}
}
var result = 0;
for (var i = 1; i <= maximum; i++)
{
if (!SumAbundantLookup(i))
{
result += i;
}
}
return(result.ToString());
}
public string Execute()
{
var pl = Primes.GeneratePrimes(1000, 10000);
var lut = new HashSet <string>();
var itemsList = new Dictionary <string, List <int> >();
foreach (var p in pl)
{
var cl = new List <char>(p.ToString().ToCharArray());
cl.Sort();
var ss = string.Join("", cl);
if (!lut.Contains(ss))
{
lut.Add(ss);
var items = new List <int> {
(int)p
};
itemsList.Add(ss, items);
}
else
{
var items = itemsList[ss];
items.Add((int)p);
}
}
foreach (var i in itemsList)
{
var valueList = i.Value;
if (valueList.Count >= 3)
{
for (var a = 0; a < valueList.Count; a++)
{
var valuea = valueList[a];
for (var b = a + 1; b < valueList.Count; b++)
{
var valueb = valueList[b];
var diff = valueb - valuea;
for (var c = valueList.Count - 1; c > b; c--)
{
var valuec = valueList[c];
var diff2 = valuec - valueb;
if (diff2 == diff && valuea != 1487)
{
return($"{valuea}{valueb}{valuec}");
}
}
}
}
}
}
return(string.Empty);
}
public string Execute()
{
//sum of a prime and 2x a square
//for every odd composite
var max = (int)Math.Pow(10, 4);
var primes = Primes.GeneratePrimes(1, max);
var primeLut = new HashSet <long>(primes);
var squares = new HashSet <long>();
for (var s = 1; s <= max; s++)
{
squares.Add(2 * (int)Math.Pow(s, 2));
}
for (var i = 3; i <= max; i += 2)
{
if (primeLut.Contains(i))
{
continue;
}
var found = false;
foreach (var p in primes)
{
if (p >= i)
{
break;
}
var diff = i - p;
if (diff > 0 && squares.Contains(diff))
{
var sq = Math.Sqrt(diff / 2);
// Debug.Print($"{i} = {p} + 2*({sq}^2)");
found = true;
break;
}
}
if (!found)
{
return(i.ToString());
}
}
return(string.Empty);
}
static void Main(string[] args)
{
double numberToOperations = -5.8;
int moduloDivide = 105;
int moduloDivideBy = 9;
int howLongPermutation = 30;
int howManyPrimes = 10;
var primes = Primes.GeneratePrimes(howManyPrimes);
Console.WriteLine("Start");
Console.WriteLine("----------");
Console.WriteLine("Round roof: " + numberToOperations);
Console.WriteLine("Result: ");
Console.WriteLine(Operations.RoundRoof(numberToOperations));
Console.WriteLine("----------");
Console.WriteLine("Round floor: " + numberToOperations);
Console.WriteLine("Result: ");
Console.WriteLine(Operations.RoundFloor(numberToOperations));
Console.WriteLine("----------");
Console.WriteLine("Fraction part: " + numberToOperations);
Console.WriteLine("Result: ");
Console.WriteLine(Operations.Fraction(numberToOperations));
Console.WriteLine("----------");
Console.WriteLine("Modulo: {0} % {1}", moduloDivide, moduloDivideBy);
Console.WriteLine("Result: ");
Console.WriteLine(Modulo.Division(moduloDivide, moduloDivideBy));
Console.WriteLine("----------");
Console.WriteLine("First {0} primes:", howManyPrimes);
Console.WriteLine("Result: ");
Primes.WriteList(primes);
Console.WriteLine("----------");
Console.WriteLine("Permutations of {0} numbers:", howLongPermutation);
Permutation.WritePermutations(howLongPermutation);
Console.WriteLine("----------");
Console.WriteLine("\n\n\n Done");
Console.ReadKey();
}
public string Execute()
{
primes = Primes.GeneratePrimes(1, 150000);
primesLut = new HashSet <long>(primes);
var sequenceCount = 4;
for (var primeIndex = 0; primeIndex < primes.Count - 1; primeIndex++)
{
var nextPrime = primes[primeIndex + 1];
var index = primes[primeIndex];
while (index < nextPrime)
{
var foundCount = 0;
for (var offset = 1; offset <= sequenceCount; offset++)
{
var value = index + offset;
if (!primesLut.Contains(value))
{
var factors = DistinctPrimeFactors(value);
if (factors.Count == sequenceCount)
{
foundCount++;
continue;
}
break;
}
}
index++;
if (foundCount == sequenceCount)
{
return(index.ToString());
}
}
}
return(string.Empty);
}